Radiation-curable resins having at least one ethylenically unsaturated group in their molecule, such as an unsaturated polyester resin, a polyurethane resin, an epoxy-acrylate resin and an unsaturated acrylate resin are extensively used in printing inks and paints. However, these resins have one great problem in that they do not have many compatible reactive diluents. Among currently used reactive diluents are high-boiling monoacrylates such as butyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate and isononyl acrylate, and polyacrylates of polyols such as neopentyl glycol diacrylate. However, these diluents are not completely satisfactory since they have a peculiar odor, irritate the skin or have other undesirable effects.
Reactive diluents suitable for use with resins having an ethylenically unsaturated group must meet the following requirements: (1) they do not irritate the skin; (2) they are highly miscible with the resin; (3) they have a high boiling point and do not evaporate easily; (4) they do not impair the radiation-curing capability of the resin; (5) they improve the film-forming property of the resin; (6) they have a low viscosity; and (7) they are inexpensive. However, no single currently available reactive diluent meets these requirements.